President Trump's son is planning to campaign against the only Republican congressman who has called for Trump's impeachment.

Donald Trump Jr. will be heading to Michigan to fight Rep. Justin Amash in a primary battle, people close to the Trump Organization executive tell CNBC.

Trump Jr.'s associates also say he will not be involved in recruiting any potential primary challenger for Michigan's 3rd Congressional District and will leave that task up to Republican Party leaders.

Donald Trump, Jr. speaks during a rally with President Donald Trump at the Williamsport Regional Airport in Montoursville, Pa., on Monday, May 20, 2019.

Tom Williams | CQ-Roll Call Group | Getty Images

Donald Trump Jr. is planning to campaign against the only Republican congressman who has called for the president's impeachment.

Donald Trump Jr. will be heading to Michigan to fight Rep. Justin Amash in a primary battle, people close to the Trump Organization executive told CNBC, speaking on the condition of anonymity. This comes after Trump's son tweeted out a poll showing Amash losing to his only challenger so far in the race, state legislator Jim Lower, and hinting he will be heading to the Wolverine state to take on the four-term lawmaker.

Trump Jr.'s associates also said he will not be involved with recruiting any of the potential primary challengers for Michigan's 3rd Congressional District, which is in the western part of the state and includes Battle Creek, and will leave that task up to Republican Party leaders.

Amash responded to the possibility of Trump Jr. working the primary by saying: "If it's what you say I love it especially later in the summer."

An Amash spokeswoman referred CNBC to his tweet and a representative for Trump Jr. declined to comment.

Tensions between Amash and Republicans loyal to President Donald Trump came to a boiling point after the Michigan representative reviewed the Mueller report and declared on Twitter that the president engaged in impeachable conduct.

Since then, he's resigned from the conservative House Freedom Caucus and lost the support of powerful financiers such as the DeVos family.

Republican Chairwoman Ronna McDaniel has also been critical of Amash's take on Mueller's findings.

Amash told CNN in March he has also not ruled out a third party bid for president in 2020.

Trump Jr.'s decision to campaign for a primary challenger could pose a larger problem for the longtime representative. Trump won his district by 10 percentage points over Hillary Clinton during the 2016 election. Michigan was also a pivotal state for his surprise victory to the White House as he just barely captured it with just under half a percentage point that year.

However, since then, the president's standing in the state has dwindled. A Morning Consult poll that regularly tracks the president's approval ratings in each state shows that 54 percent of those polled in Michigan disapprove of his job in office, while 42 percent approve.